1. Field of the Invention
This invention relates to the field of fluid mixing, and more specifically, to an apparatus and method for mixing fluids at the surface for the treatment of subterranean conditions.
2. Description of the Related Art
A variety of methods and apparatus have evolved for the purpose of treating oil and gas well formations intended to modify the well bore in-flow characteristics of marginally producing wells. The majority of these apparatus and methods involves positioning a work-over rig over the wellhead and installing and/or removing downhole tubing and equipment to be able to reach the formation with the chemicals. This downhole equipment provides adequate delivery at the expense of long well downtimes and high treatment costs. These factors prevent the use of these apparatus and methods for treatment of marginal producing wells whose incremental production economics are unfavorable for expensive treatments.
For marginal producing wells, the prior methodology involves either injecting the chemicals directing into the flow lines or mixing treatment chemicals in truck-mounted tanks for injection into the formation. Both methodologies result in poor intermixing of the chemicals, and neither method offers a safe way to heat flammable solvents and chemical inhibitors prior to injection.
An additional problem associated with mixing carrier fluids and chemicals in truck-mounted tanks is that oilfield water hauling trucks and tanks are routinely used for many applications that do not leave the empty tank clean after the job is done. If a solvent or inhibitor is mixed with carrier fluid inside the tank, the residue from the previous job may be dispersed within the water or oil that is used as the carrier fluid. This can result in a significant reduction in the effectiveness of the solvents and/or inhibitors that are used.
The fluid systems employed for marginal formation treatment typically consist of a carrier fluid in which a chemical is mixed. Carrier fluids employed for formation treatment are generally produced fluids, such as produced water, crude oil, or natural gas condensates. These fluids are often heated to reduce fluid viscosity and improve formation penetration.
The chemicals used for treatment include solvents, inhibitors, polymers, acids, and wetting agents. Each of these must be well mixed to be effective. For example, polymerization for sand control involves mixing a catalyst agent with a resin, which results in a highly exothermic reaction that produces the polymer that binds the sand grains together to form a permeable boundary near the well bore. Pre-mixing these chemicals requires temperature control methods to chill the fluids and prevent hazardous conditions in the mix tanks. Mixing these reactants in-situ often results in poor performance due to inadequate mixing in the formation.
Marginal wells often suffer from materials plugging of the formation. These plugging foulants may be paraffins in certain crude oil fields, minerals in water flood fields, or hydrates in natural gas fields. Paraffinic foulants are typically treated with chemicals mixed with a hot oil carrier fluid to liquify the paraffin and keep it in solution as it is carried out of the formation. Mineral foulants are treated with acid mixed into a water carrier. Corrosion inhibitor is added to the mixed solution to protect the well tubing string from the acid. It has been previously documented that hydrate blocking may be dissolved using heated carrier fluids and solvents along with various chemicals to inhibit the reformation of the hydrate.
The present invention solves these and other problems by effectively, cleanly and safely mixing chemicals with the carrier fluid at the surface and injecting the mixture down the well bore. Several objects of this invention are listed below.
It is an object of the present invention to improve daily production operations performance and reduce maintenance costs in oil and gas field projects.
It is a further object of the present invention to provide a means for mechanically mixing fluids in a field setting.
Yet another object of the present invention is to offer controlled mixing and proportioning of fluids that vary in temperature, viscosity and density.
It is a further object of the present invention to provide a safe method of heat exchange by injecting solvents and inhibitors into a heated stream of carrier fluid.
Yet another object of the present invention is to allow more than one chemical to be injected and effectively mixed in the carrier fluid.
It is a further object of the present invention to enable the mixing of carrier fluids and chemicals in a clean environment so as to avoid residue from previous jobs.
Yet another object of the present invention is to provide a means for dealing effectively with in-situ mineral scale deposition, paraffin buildup, metal sulfide plugging, water and condensate banking, methane hydrate blocking, and emulsion blocking, among other problems.
It is a further object of the present invention to improve the mixing of drilling additives used to control bore hole stability in the water well drilling industry.
Yet another object of the present invention to offer a fluid mixing apparatus that is portable.
It is a further object of the present invention to offer a mixing apparatus and a stimulation method that are economically viable for marginal well operations.